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Báo cáo khoa học: Light regulation of CaS, a novel phosphoprotein in the thylakoid membrane of Arabidopsis thaliana

Exposure ofArabidopsis thalianaplants to high levels of light revealed specific phosphorylation of a 40 kDa protein in photosynthetic thylakoid membranes. The protein was identified by MS as extracellular calcium-sensing receptor (CaS), previously reported to be located in the plasma membrane. | ỊFEBS Journal Light regulation of CaS a novel phosphoprotein in the thylakoid membrane of Arabidopsis thaliana Julia P. Vainonen1 Yumiko Sakuragi2 Simon Stael1 Mikko Tikkanen1 Yagut Allahverdiyeva1 Vímí PaQl l aKỈnQn A 1 o riijij 0 o c I I -X t Q a 1 1 1 zt n rĩ f Cn ho I Io f2 Ạ lovo n lo r onoK3 Virpi Paakkarinen Eveliina Aro Marjaana Suorsa Henrik V. Scheller Alexander V. Vener and Eva-Mari Aro1 1 Department of Biology Plant Physiology and Molecular Biology University of Turku Finland 2 Department of Plant Biology Faculty of Life Sciences University of Copenhagen Denmark 3 Department of Clinicaland ExperimentalMedicine Faculty of Health Sciences Linkoping University Sweden Keywords high light protein phosphorylation STN8 kinase stress response thylakoid membrane Correspondence E.-M. Aro Department of Biology Plant Physiology and Molecular Biology University of Turku FI-20014 Turku Finland Fax 358 2 333 5549 Tel 358 2 333 5931 E-mail evaaro@utu.fi Received 18 December 2007 revised 7 February 2008 accepted 13 February 2008 doi 10.1111 j.1742-4658.2008.06335.x Exposure of Arabidopsis thaliana plants to high levels of light revealed specific phosphorylation of a 40 kDa protein in photosynthetic thylakoid membranes. The protein was identified by MS as extracellular calcium-sensing receptor CaS previously reported to be located in the plasma membrane. By confocal laser scanning microscopy and subcellular fractionation it was demonstrated that CaS localizes to the chloroplasts and is enriched in stroma thylakoids. The phosphorylation level of CaS responded strongly to light intensity. The light-dependent thylakoid protein kinase STN8 is required for CaS phosphorylation. The phosphorylation site was mapped to the stroma-exposed Thr380 located in a motif for interaction with 14-3-3 proteins and proteins with forkhead-associated domains which suggests the involvement of CaS in stress responses and signaling pathways. The knockout Arabidopsis lines revealed a significant .